Establishment of woody savannah species on various mined substrates: Toward rehabilitating self sustaining plant communities at Navachab Gold mine
Loading...
Date
2015
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
For many years mining has been a vital component of the development of many countries. Although an important income generator, mining is one of the factors that affect biodiversity and ecosystems.There is an increase in the intensity of environmental damage caused by mining over the years, and thus an increased need to rehabilitate the disturbed ecosystems. The success of any rehabilitation project requires an ecological understanding of natural indigenous vegetation communities. This project investigated the potential use of mined substrates to establish indigenous savannah woody species. The main objective of this project was to investigate the establishment of indigenous vegetation on mined substrates and develop an understanding of species assemblage and habitat preference in the Karibib thorn bush savannah. The main objective has been set to contribute scientific information to the development of methodologies for using mined substrates to establish self-sustaining, indigenous plant communities and to the development of mine closure and rehabilitation plans. To accomplish this goal, three studies as summarized below were carried out in the form of this MSc.
The first study determined the plant communities and their habitats in the surrounding and around undisturbed ecosystems in the Karibib thorn bush savannah. Here, a vegetation survey was carried out in five undisturbed habitats namely; Marble hills, Sandstone hills, Granite hills, Calcrete plains and Kalahari red sand plains. Walking belt transects were used to collect community data and soil samples were collected in each habitat. Species diversity, composition, evenness and richness were determined for each habitat. Ordinations and correlations were used to determine the relationships between plant species and soil variables and niche breadth for each plant species was determined to show the degree of specialization for each species. Ordinations of woody vegetation in the Karibib thorn bush savannah indicated that there were fairly distinct species assemblages. Identified species assemblages were related to soil properties. The second study investigated the germination requirement of eight selected woody species to determine the best seed treatment for each species. Sulphuric acid, acetone and hot water scarification methods were used. For each species, there were significant differences in germination percentage between different seed treatments. Sulphuric acid improved germination in all the species, acetone also improved germination in six species, while hot water improved germination in only two species.
The preceding studies provided context for the main study which investigated the establishment of woody savannah species on various mined substrates, since establishment of vegetation requires the knowledge of species assemblages, habitat preferences as well as germination requirements. Much research has been done on native species on mine land rehabilitation but few studies have correlated native species establishment with mined substrates properties. The third study therefore assessed the suitability of various mined substrates for the establishment of indigenous savanna species and explored which properties make a particular substrate suitable for plant growth. Seven selected species grown from seeds in the nursery were used in this study. Seedling growth and survival was monitored for twelve months in different mined substrates. Growth and survival were correlated and ordinated with substrate chemical and physical properties. Results showed a significant difference in the average growth and survival of seedlings between different species (d.f=6, F=99.779, p<0.001) and different substrates (d.f=8, F=21.457, p<0.001) and provide evidence that some species had high survival and high growth in most of the substrates (Acacia senegal, Acacia tortilis and Acacia erioloba). On the contrary, some species had high survival and low growth in most of the substrates e.g Acacia reficiens. Other species had both poor growth and survival in most of the substrates e.g Catophractes alexandri and Acacia erubescens. Though species showed differences in growth and survival performances, all species grew to some extent in each substrate. The project successfully established knowledge on the germination requirements for various savannah species in the Karibib thorn bush savannah. It is crucial to understand the germination requirements of plant species to ensure their successful establishment. The study further indicated the influence of soil properties on the distribution patterns of woody species in the Karibib thorn bush savannah. This was revealed by Canonical Correspondence Analysis (CCA) ordination, showing several tight species groupings which indicated that many species were unique to a single habitat or had a relatively high abundance in a particular habitat. The findings on plant and soil relations in the study area will help in the selection of adaptable species for improving and rehabilitating disturbed arid environments. Furthermore, the study established that the selection of suitable species and substrates to use in rehabilitation projects should be evaluated in terms of both growth performance and survival performance. After all, a suitable substrate will allow species to grow and survive. Similarly, useful suitable species to be used must be able to grow and survive in a range of substrates. The study has therefore built a foundation for future restoration and rehabilitation projects.
Description
A thesis submitted in fulfilment of the requirements for the Degree of Master of Science
Keywords
Woody Savannah species, Mined substrates, Plant communities, Navachab gold mine